I. Field
The following description relates generally to wireless communications, and more particularly to a pilot design and centralized scheduling for dynamic SIMO, SU-MIMO and MU-MIMO mode of operation for reverse link transmissions.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems; time division multiple access (TDMA) systems; frequency division multiple access (FDMA) systems and orthogonal frequency division multiple access (OFDMA) systems; 3rd Generation Partnership Project 2 Ultra Mobile Broadband (UMB); and 3rd Generation Partnership Project Long Term Evolution (LTE) systems. Generally, each terminal communicates with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from a base station(s) to a terminal(s), and the reverse link (or uplink) refers to communication from a terminal(s) to a base station(s). These communication links may be established via single and/or multiple receive/transmit antennas at base stations or terminals.
Additionally, in wireless communications a majority of spectrum bandwidth, as well as base station transmit power, is regulated. Design around such constraints has led to multiple-input multiple-output (MIMO) systems as a path toward realizing increased peak data rate, spectral efficiency, and quality of service. A MIMO system consists of transmitter(s) and receiver(s) equipped, respectively, with multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A variant of a MIMO system that still presents gains compared to single-input single-output (SISO) systems is a single-input multiple-output (SIMO) system. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NV independent channels, which are also referred to as spatial eigenchannels, where 1≦NV≦min {NT,NR}.
MIMO systems can provide improved performance (e.g., higher throughput, greater capacity, or improved reliability, or any combination thereof) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. It should be appreciated that although SIMO systems afford a somewhat lesser improvement in performance, such systems avoid complexity at the receiver, by employing only a single antenna in the user equipment and relying on multiple antennas at base stations. MIMO systems can be divided in two operational classes: (i) Single-user MIMO, and (ii) multi-user MIMO. A main goal of single-user MIMO (SU-MIMO) operation can be to increase peak data rate per terminal, whereas a main goal in multi-user MIMO (MU-MIMO) can be to increase sector (or service cell) capacity. Operation in each of these classes has advantages. SU-MIMO exploits spatial multiplexing to provide increased throughput and reliability, MU-MIMO exploits multi-user multiplexing (or multi-user diversity) to further gains in capacity. Additionally, MU-MIMO benefits from spatial multiplexing even when user equipment has a single receiver antenna.
To benefit from the improved performance derived from the MIMO paradigm of wireless communication, while servicing simultaneously SIMO, SU-MIMO, and MU-MIMO users without detriment to any of such modes of operation, there is a need for a systems and methods that provide for a unified and centralized, as well as a dynamic, scheduling of SIMO, SU-MIMO, and MU-MIMO transmissions.